The present invention relates generally to a plasma processing method for carrying out a plasma processing, such as an electron cyclotron resonance (ECR) treatment, with respect to a substrate to be treated, such as a semiconductor wafer, to form and etch a thin film, such as an SiO2 film or a fluorine containing carbon film.
In order to achieve the high density integration of semiconductor devices, it has been developed to provide devices with scale down of patterns and multilayering of circuits. As one of such devices, there is a technique for multilayering wiring. In order to provide a multilayer metallization structure, a number n wiring layer and a number (n+1) wiring layer are connected to each other by means of a conductive layer, and a thin-film called an interlayer dielectric film is formed in a region other than the conductive layer. Typical interlayer dielectric films are SiO2 and SiOF films. These films are formed by means of a plasma processing system for carrying out the ECR plasma processing, which is shown in, e.g., FIG. 11.
For example, in this system, a microwave of, e.g., 2.45 GHz, is supplied into a plasma producing chamber 1A via a waveguide 11, and a magnetic field of, e.g., 875 gausses, is applied thereto. The interaction (the electron cyclotron resonance) between the magnetic field and the microwave activates a plasma gas, such as Ar gas or O2 gas, and a thin-film deposition gas, such as SiH4 gas, which is introduced into a thin-film deposition chamber 1B as plasmas to form a thin film on a semiconductor wafer W which is mounted on a mounting table 12.
By combining a main electromagnetic coil 13, which is provided so as to surround the plasma chamber 1A, with an auxiliary electromagnetic coil 14, which is provided on the bottom side of the thin-film deposition chamber 1B, the magnetic field extends downward to be applied from the plasma chamber 1A to the thin-film deposition chamber 1B. In addition, in order to improve the uniformity of the quality of the film, the positions and current values of the main electromagnetic coil 13 and the auxiliary electromagnetic coil 14 are adjusted so that the magnetic flux density on the surface of the wafer W is substantially uniform, thereby producing uniform plasma.
In actual process, a treatment called a preheat is generally carried out after the wafer W is mounted on the mounting table 12. If the thin-film deposition treatment is carried out by introducing the thin-film deposition gas immediately after a wafer W of ordinary temperature is mounted on the mounting table 12, the temperature of the wafer W does not rise to a predetermined temperature, which is set during the thin-film deposition, although the wafer W is heated by plasma. Thus, the thin-film deposition proceeds at a lower temperature than an intended temperature, so that a thin film having a bad quality is formed. In order to prevent this, the preheat treatment is carried out.
Specifically, before the thin-film deposition gas is introduced after the wafer W is mounted on the mounting table 12, a plasma is produced to heat the wafer W to a predetermined temperature, e.g., a thin-film deposition temperature, and then, the thin-film deposition gas is introduced to carry out the thin-film deposition treatment. At this time, the preheat and the thin-film deposition treatments are carried out by producing plasma, which has been considered to be optimum in the thin-film deposition, without changing any parameters of the microwave and magnetic field.
However, in the above described method, a uniform plasma is produced in the vicinity of the wafer W so as to be suited to the thin-film deposition, so that the magnetic flux density is expanded. Therefore, the total heat gain is small although the heat gain per unit area is uniform. Therefore, it takes a lot of time from the point of view of the preheat. For example, even if a plasma is produced immediately after the wafer W is mounted, it takes about 60 seconds to raise the temperature of the wafer W from 80xc2x0 C. to 400xc2x0 C., which is the thin-film deposition temperature, so that there is a problem in that the total throughput deteriorates.
It is therefore a principal object of the present invention to eliminate the aforementioned problems and to provide a plasma processing method capable of shortening a preheat time.
It is another object of the present invention to provide a plasma processing method capable of improving the uniformity of the quality of each of various kinds of thin films when the thin films are deposited.
It is a further object of the present invention to provide a plasma processing method capable of shortening the time required to carry out a post treatment, such as the removal of an etching gas and a resist film after etching.
It is a still further object of the present invention to provide a plasma processing method capable of shortening the time required to carry out a pretreatment, such as the removal of a natural oxide film which is formed on the surface of a substrate.
Therefore, the present invention is characterized by a plasma processing method for supplying a microwave into a vacuum vessel by high-frequency producing means and for forming a magnetic field in the vacuum vessel by magnetic field forming means to produce a plasma in the vacuum vessel by the electron cyclotron resonance between the microwave and the magnetic field to treat a substrate to be treated with the produced plasma, the method comprising: a first step of introducing the substrate into the vacuum vessel and for producing a plasma to heat the substrate; and a second step of activating a thin-film deposition gas in the vacuum vessel as a plasma which forms a thin film on the substrate, wherein the shape of the magnetic field is changed by setting the current values of the magnetic field forming means at the first and second steps to be different from each other so that the magnetic flux density on the substrate during the production of the plasma at the first step is greater than that at the second step.
In addition, the present invention is characterized by a first thin-film deposition step of activating a first thin-film deposition gas in the vacuum vessel as a plasma which forms a first film on the substrate, and a second thin-film deposition step of activating a second thin-film deposition gas in the vacuum vessel as a plasma which forms a second film on the first film, wherein the current values of the magnetic field forming means at the first and second thin-film deposition steps are set to be different from each other to change the shape of a magnetic field.
Moreover, the present invention is characterized by an etching step of activating an etching gas in the vacuum vessel as a plasma which etches the substrate, and a post-treatment step of activating a post-treating gas in the vacuum vessel as a plasma which carries out a post-treatment, wherein the shape of the magnetic field is changed by setting the current values of the magnetic field forming means at the etching and post-treatment steps to be different from each other so that the magnetic flux density on the substrate during the production of the plasma at the post-treatment step is greater than that at the etching step. The post-treatments herein include a treatment for removing the residual of an etching gas and a treatment for ashing a resist film with oxygen gas.
In addition, the present invention may be characterized by an etching step of activating an etching gas in the vacuum vessel as a plasma which etches a natural oxide film on the surface of the substrate, and a thin-film deposition step of activating a thin-film deposition gas in the vacuum vessel as a plasma which forms a thin film on the surface of the substrate, wherein the shape of the magnetic field is changed by setting the current values of the magnetic field forming means at the etching and thin-film deposition steps to be different from each other so that the magnetic flux density on the substrate during the production of the plasma at the etching step is greater than that at the thin-film deposition step.
Moreover, the present invention may be characterized by a first etching step of activating an etching gas in a vacuum vessel as a plasma which etches the substrate, and a second etching step of further etching the substrate by the plasma after the first etching step, wherein the shape of the magnetic field is changed by setting the current values of the magnetic field forming means at the first and second etching steps to be different from each other so that the isotropy of etching with respect to the surface of the substrate at the second etching step is higher than that at the first etching step. The shape of the magnetic field at the first etching step may be the shape of a mirror magnetic field, and the shape of the magnetic field at the second etching step may be the shape of a divergent magnetic field.